Python 3.2错误“UnboundLocalError: 在赋值前引用了局部变量”

Question

我现在正在制作一个2D游戏，玩家可以使用不同的枪，每把枪的射击速度都不一样。当我尝试为每把枪设置不同的射击速度时，出现了一个错误：

if currentTime - bulletGap >= 2 and bulletType == "pistol": # 2 seconds between bullets
UnboundLocalError: local variable 'bulletGap' referenced before assignment

我在使用这些变量的函数之前定义了“bulletGap = 0”和“gunFire = [True, True, True]”，但是我还是遇到了错误。下面是其余的（不工作的）代码。

def __init__(self, x, y, velx, vely, direction, bulletType):

    currentTime = pygame.time.Clock()

    if currentTime - bulletGap >= 2 and bulletType == "pistol": # 2 seconds between bullets
        bulletGap = pygame.time.Clock()
        gunFire[1] = True
        return

    elif currentTime - bulletGap >= 4 and bulletType == "shotgun": # 4 seconds between bullets
        bulletGap = pygame.time.Clock()
        gunFire[2] = True
        return

    elif currentTime - bulletGap >= 0.5 and bulletType == "automatic": # 0.5 seconds between bullets
        bulletGap = pygame.time.Clock()
        gunFire[3] = True
        return

    self.type = bulletType
    self.direction = direction
    self.velx, self.vely = velx, vely

    for n in range(gunFire):

        if gunFire[n] == True:

            if direction == "north":

                south = pygame.transform.rotate(Bullet.bulletImage[bulletType], 90)
                self.image = pygame.transform.flip(south, False, True)

            elif direction == "east":

                self.image = pygame.transform.flip(Bullet.bulletImage[bulletType], True, False)

            elif direction == "south":

                self.image = pygame.transform.rotate(Bullet.bulletImage[bulletType], 90)

            elif direction == "west":

                self.image = Bullet.bulletImage[bulletType]

            pygame.Rect.__init__(self, x, y, Bullet.width, Bullet.height)

            Bullet.bulletList.append(self)
            break

另外（顺便问一下），在if语句后面我还需要“return”吗？这些是我之前写的代码留下的，我试着把它们去掉，但还是出现了同样的错误。

Answer 1

假设你的代码大概是这样的：

class C:
  bulletGap=0
  def method(self):
    print(bulletGap)  # or any sort of reference
    bulletGap = 1     # or any sort of assignment

c=C()
c.method()

那么你需要使用 self. 来正确地引用 bulletGap：

class C:
  bulletGap=0
  def method(self):
    print(self.bulletGap)
    self.bulletGap = 1  # If bulletGap is instance-specific
    C.builletGap = 1    # If bulletGap is class-specific

c=C()
c.method()